Abstract

Dynamic interactions between cancer cells and their surrounding microenvironment influence tumor survival, growth and metastasis. The tumor microenvironment harbors a complex variety of cells including T lymphocytes and macrophages that produce a host of cytokines, chemokines, growth factors or interleukins, all of which presumably work in coordination to determine net tumor biology. Immune cells can offer a critical check-point in tumor progression. Interestingly however, infiltration of the tumor by immune cells appears to have dual functionality - they can reportedly either be pro-metastatic or anti-metastatic in their contribution. These clearly conflicting roles of immune cells limit our comprehension of their actual input to tumor advancement. Tumor infiltrating lymphocytes, in particular, the infiltration by T cells, has emerged as a good prognostic marker for a variety of cancers. However, the key molecular factors that regulate the cross-talk between tumor cells and T lymphocytes, and the underlying signaling pathways are still ill-defined. Moreover, the impact of T lymphocytes of the inflammatory tumor microenvironment, on the epithelial-mesenchymal plasticity and associated metastatic traits in breast cancer cells, is incompletely understood. We previously demonstrated that two key EMT/CSC factors - FOXC2 and Twist - are critical requirements for breast carcinoma cells to metastasize. The objective of the current study is to systematically investigate the role of regulatory T cells in EMT/CSC-dictated breast tumor progression, using two isogenic breast cancer cell lines (67NR and 4T1) that form primary mammary tumors similarly, but differ drastically in their ability to metastasize.